Corre.spondeuce — Prof. E. JD. Cope. 527 



cingulnm, quite distinct from the rest of the crown, in Esthovyx, 

 •which is absent in MioJoplius, according to Owen. Though this 

 is not a]one a generic character, in my opinion it is one of those 

 indicators which generally accompany thorn. In like manner, Mio- 

 lophvs presents no important distinction from Deltatharium, but the 

 wide internal lobes of the crowns lead me to suspect that such exist. 

 As to the name PlatycTioerops, it cannot be adopted, as its publica- 

 tion was not accompanied by the distinct generic description which 

 the accepted rules of nomenclature require. E. D. Cope. 



THE EATEACHIAi OF THE PEEMIAN BEDS OF BOHEMIA. 

 SiK, — In Dr. Fritsch's volume we have the continuation of an ex- 

 tensive work which I have noticed at various times in the "Is'aturalist " 

 as tlie successive parts appeared. I desire to add, on this occasion, 

 my renewed commendation of the care and detail with which Dr. 

 Fritsch continues to develope the subject, and my praise for the 

 admirable plates which accompany the text. The species treated of 

 are those which belong to the larger forms of the Rhachitomi, 

 together with some of the intermediate types, such as the Dendrerpe- 

 tonidge. Of the greatest interest are two new genera of the order 

 Embolomeri, Chelydosaurus and SpJienosaurus, where the additional 

 vertebral centrum, entire in the type of the order (Cricotus), is 

 divided into three segments, two lateral and an inferior. This is a 

 curious discovery, especially as Sphenosaiirus has hitherto been 

 regarded as a reptile.^ It also has an important bearing on the value 

 of the order Embolomeri, which Dr. Fritsch is disposed (p. 4) to 

 question. He thinks that the embolomerous A'ertebral structure is 

 confined to the caudal region in the genus Cricotus, although I have 

 figured it in the lumbar and cervical region of that genus, and 

 described it as found in the dorsaP region. Dr. Fritsch reached this 

 conclusion because he finds that in Arcliegosaurus the caudal region 

 is embolomerous, and the dorsal region rhachitomous. His discovery 

 of the persistence of the embolomerous condition in the dorsal region 

 of Chelydosavrus and SpJienosaurus might have suggested to hira the 

 correctness of my observations on Cricotus. I add here that in 

 Eryops, in which the dorsal vertebra are rhachitomous, the caudal 

 vertebrae are not embolomerous. So Arcliegosaurus stands alone in 

 this respect. This determination of the characters of Archegosniirus 

 by Dr. Fritsch is very useful to American paljeontologists, as it has 

 hitherto been very imperfectly descriV)ed. I have stated that there 

 are vertebrse of this type from Lebach in the Museum of Princeton 

 College, New Jersey. As they agree exactly with Dr. Fritsch's 

 figures of Arcliegosaurus, it is difficult to perceive why he denies the 

 accuracy of my statement in the matter (p. lo). E. D. Cope. 



[Ee-published at the writer's request from the American Naturalist, June, 1885 ] 



^ Fauna der Gaskohle in d. Kalksteinen d. Permformation Bohmens. Von Dr. 

 Anton Fritsch, b. ii. heft i. ; Praag, 1885. 



'■* These two genera should form a second family of the Embolomeri, characterized 

 as above, which I call the Spheiiosaurida3. 



3 Proc. Amer. Philo. Soc. 1884, p. 29. 



